Bottlebrush polymers have found widespread applications in fields ranging from drug delivery and molecular imaging to novel materials and stimuli responsive networks.1-3 Graft-through ring-opening metathesis polymerization (ROMP) offers distinct advantages over other bottlebrush synthesis methods.4,5 The fast-initiating Grubb's 3rd generation catalyst (G3-Cat) has been shown to sustain propagation of polymer chain reactions with exceptionally high tolerance towards a wide range of sterically-hindered multivalent macromonomers (MMs), reaching high degrees of polymerization and low dispersity values, even at low millimolar concentrations.6,7 Furthermore, using G3-Cat, it is possible to control composition, morphology, and size of final macromolecules, allowing the preparation of remarkable polymeric architectures, such as bottlebrush polymers and star polymers.7-11 Due to the high packing density of their side-chains, the backbones of bottlebrush polymers are very rigid and adopt extended morphologies with minimal side-chain entanglement.6 Recently, self-assembly behaviors of bottlebrush block copolymers (BBCPs) have become an active area of research, as these macromolecules readily undergo phase separation and can be used to design materials with novel mechanical properties in bulk.6,12 
Polymeric star nanoarchitectures, on the other hand, offer several different valuable features, such as tunable nanoscale sizes and shapes that mimic globular biomacromolecules, allowing for extended blood circulation and efficient biodistribution and/or tumor accumulation.13-15 These properties make star polymers particularly well-suited for biological applications.10 
The development of bottlebrush and star polymeric structures (e.g., brush-arm star polymers (BASPs)) is a growing field of research because these polymeric structures have broad applications. Previous work has reported preparation of multi-component MMs that can be used in graft-through ROMP; these MMs contain side-chains with a multitude of functions and properties, which can either be on different MMs, or branching off the same MM.9,11,12,14,16,17 In particular, the branched platform consists of a ROMP-compatible norbornene group on a molecule that also contains two orthogonally functionalizable sites: an alkyne, for which copper (I)-catalyzed alkyne-azide cycloaddition (CuAAC) can be applied,18-20 and a carboxylic acid group, compatible with carbodiimide coupling chemistry,21-25 both of which are efficient, and known modes of conjugations. The side-chains can be functionalized with two dissimilar polymers that self-assemble into various morphologies or a polymer chain containing an agent (e.g., a therapeutic agent (e.g., drug), a diagnostic agent (e.g., imaging agent), a prophylactic agent, or a biological ligand); resulting polymers are reported to demonstrate interesting characteristics across multiple applications, including self-assembly, drug delivery, and molecular imaging.8,9,11,26-28 